A known method of cleaning a dirty gas is to pass the dirty gas through a packed particulate bed through which a liquid (usually water) passes in the opposite direction to the gas. This known method of gas cleaning has a number of disadvantages. Among these disadvantages are:
(a) the method cannot be used to treat gases which are polluted with particulate material, or with pollutants which form precipitates with water or the washing liquid; and PA1 (b) as the cleaning operation proceeds, the high initial efficiency of the process is reduced due to collection of pollutants in the bed, dense packing of the bed, formation of channels in the bed, and the like. PA1 (a) passing the dirty gas upwards through a bed of particulate material, while passing a wash liquid downwardly through the bed; and PA1 (b) extracting particles from the lower region of the bed by entrainment of such particles in an upward-moving stream of clean gas, and depositing the entrained particles on the top of the bed. PA1 (a) a particulate bed; PA1 (b) means for feeding the dirty gas into the particulate bed; PA1 (c) means for supplying a clean gas to a region of the bed for upwards passage of the clean gas therethrough; and PA1 (d) means for supplying a wash liquid to the upper region of the particulate bed.